The Power of Souls
by Heaven The Angel
Summary: Almost two weeks after the monsters returned to the surface, it is almost time for Sans' 18th birthday and Frisk and the others want to answer the one question that hasn't been answered; where did Sans and Papyrus come from? When Flowey and Chara finally get their powers back and the gang has to go into the depths of Timespace to stop them, they might finally get their answer.
1. Prologue

Prologue

August 22, 201X

Dear Journal,

Well it is almost time.

I can t believe it has been almost 15 years since the incident. I d rather not talk about it right now; it just brings back too many horrible memories. However, I just can t wait to see them again! I want to see how they ve changed! I want to see what they ve learned! I want to see if he finally did it! Oh if he finally was able to do it all of my hard work will be worth it.

I just cannot take it any longer!

I must know if he did it!

Then my theory would be confirmed and everyone will see the TRUE power of souls. If he can just unlock the last one, all of the souls together might just bring peace once and for all!

Sans, Papyrus, if either of you are reading this you MUST remember what I just wrote down! You MUST unlock the power of your souls in order to restore true peace between humans and monsters.

I believe in you my sons.


	2. Chapter 1

Chapter 1

The time is almost here.

In just one minute, the event will finally be taken place.

He's been waiting for this day since as long as he can remember.

The clock is ticking.

10…

9…

8…

7…

6…

5… Almost there.

4… The time is coming.

3… It's happening!

2… This is going to be the most amazing moment of his entire life!

1…

"HAPPY BIRTHDAY!"

Sans roughly woke up to the sound of banging on drums and loud kazoos playing the birthday song. Sans tiredly rubbed his eyes and saw that it was all his friends who were making the ruckus. Frisk was simply playing a kazoo, Toriel was holding a large birthday pie with whipped cream and two candles (one that had the number "1", and one that had the number "8"), Undyne was violently banging on a gigantic drum with wooden drum sticks, Dr. Alphys was holding a digital device in her hand that showed a gigantic hologram that said "Happy Birthday!", and his royal highness, King Asgore, was wearing his usual flower shirt and simply played the French horn. They all seemed to be so passionate about his birthday, but his brother, Papyrus, showed off the most.

He was holding a humongous drum in front of him and banging on it with his one of his hands while also playing a French horn with his other hand (off key, of course). Papyrus was also dancing around the room as if the drum was as light as a feather, showing that he was definitely excited for his brother.

"HAPPY BIRTHDAY, SANS!" Papyrus said in his exaggerated, high-pitched voice. Sans said, while stretching his arms "heh, mornin' bro. thanks for the…really loud wake-up." Papyrus happily replied "YOU'RE WELCOME!"

It was one of these moments that Sans was so grateful to have Papyrus as a brother. He's always so ecstatic about special events, especially his birthday. Papyrus would both make loud, uncoordinated music with random kitchen utensils and stuff that he just happened to find around the house or make him an inedible spaghetti birthday cake.

This year…he did both.

"wow, the cake looks really good this year, pap! it actually looks edible this time." Papyrus, unaware that that was sort-of an insult, put on a smile, and placed the frozen spaghetti cake on Sans' drawer while Undyne spoke up. "Why, of course it does! That's because I helped him make it! But…to be fair…the first one we made was WAY better than this one." Sans sat up on the bed and asked "oh, really? how so?" Undyne put her scaly hands on her hips and replied "Well, I basically ruled, about, 75% of that version of it. Did you know that if you tap a certain part of the stove at exactly the right moment…you can blow up an entire house?!" Toriel turned to King Asgore and Toriel with nervous sweat on her forehead. "This uh…reminds me." Undyne pulled out her new phone that Dr. Alphys made for her, swiped it a couple time and showed it to Asgore. What he saw…was not surprising to say the least.

"Yea…I may need a new house…again." Undyne her head to Sans and continued "Oh! And I also made homemade noodles that time!"

Asgore didn't get angry (even though she's done this, like, ten times), instead, he simply sighed and said "I'll go get the construction crew." But, as Asgore was planning to leave, Toriel grabbed his shoulder and turned him around, making him meet with Toriel's oh-so-famous glare. "You are NOT going to leave this house! You can call your construction crew later; right now, we are going to celebrate our good friend's birthday!" Sans turned to Toriel and her ex-husband and said "it's alright, your majesty. you can go fix undyne's house. i'll be fine here." Toriel turned to him and said "No, Sans! This is you're 18th birthday! When you turn 18 you finally move from teenager to young adult. So, it is QUITE a big deal." Sans got up from his bed and insisted to Toriel "well, for some reason, you decided to make this huge surprise to me two days before my ACTUAL birthday. so, for now, i'm still 17. it's fine, really." Sans could tell Toriel wanted to protest incredibly badly, but, after a couple of seconds, she closed her eyes, breathed in, breathed out, and then turned to Asgore.

"Fine! You may go fix Undyne's house. But after you're done, make sure you go straight back here! Understand?" Asgore said to her "Well, can't I at least get a donut or-" Toriel gave him and glare again. "Understand, Asgore?!" Asgore arched his back away from her with scared eyes. "Uh…Well, gotta go!" Then, he finally left the room and soon went out of the house.

Sans turned to Papyrus and asked "speaking of…why'd you guys prepare this two days before?" Papyrus happily put his drum on the ground while replying "WELL, HER MAJESTY TORIEL HAS AN ENORMOUS POINT! I WANT TO MAKE THIS BIRTHDAY THE MOST ENJOYABLE, AND DELECTABLE BIRTHDAY THAT ANY MONSTER AND HUMAN HAS EVER KNOWN! I'VE ALREADY PLANNED MUFFET TO MAKE YOU FIVE BIRTHDAY CAKES AND TEN BOXES OF COOKIES AND DONUTS (HALF OF WHICH MAY BE FOR ME). SO, DO NOT FRET, MY PRECIOUS BROTHER! YOU ARE GOING TO HAVE THE BEST BIRTHDAY EVER! I'LL MAKE SURE OF IT!" Sans smiled at his brother's enthusiasm and said "aww...thanks papyrus…you're the best brother anyone could ask for!" Sans walked up to his taller brother and hugged him, and after a second, Papyrus smiled and hugged back. Everyone in the room awed at the adorable brotherly moment.

Suddenly, they heard something vibrate, which apparently came from Mettaton. Noticing the vibration on his metallic wrist, he looked at it and noticed that his watch was vibrating with the hands saying 9:00. Mettaton immediately vibrated along with the watch and yelled "AHH! I'M GOING TO BE LATE FOR MY PERFORMANCE AT THE RETIREMENT HOME, AND MY MORNING NEWS, AND MY REENACTMENT OF 'ROMEO AND JULIET' AT THE GIRL SCOUTS!" Mettaton quickly rushed out of the room with Toriel holding out her hand while yelling "Mettaton, wait!" But he was already gone. Dr. Alphys quickly got more sweaty than usual and said "U-Um…I'm s-sorry Sans…I g-gotta go t-take care of Mettaton. He g-gets REALLY cranky w-when he misses a p-performance. H-Happy birthday!" She quickly went out of the room with Toriel once again trying to stop her. Then, Undyne said "Well, if I know anything about Alphys, is that she can drown her entire lab in sweat if she doesn't stop. And I don't want a sweaty girl hugging me all the time! Need to go calm her down." Toriel said "Don't you dare-" But Undyne was already after Dr. Alphys and Mettaton. Toriel had no choice but lean down to Frisk and quietly say "I'll return as soon as I can, my child. Don't worry about a thing." Then she suddenly changed her tone and yelled "COME BACK HERE AND CELEBRATE THIS MOMENTOUS OCCASION!" She quickly went out of the room as well, leaving only Papyrus, Sans, and Frisk alone in the room.

Papyrus turned to Sans and said "WELL…THAT WAS STRANGE. BUT GOOD NEWS IS WE GET TO SPEND SOME TIME TOGETHER! THIS IS YOUR FIRST DAY OF YOUR FINAL DAYS OF BEING SEVENTEEN! WHAT DO YOU WANT TO DO NOW?!" Sans, despite his brother enthusiastic behavior, replied "well…i wouldn't mind going back to sleep."

Surprisingly (possibly the biggest surprise so far today)…Papyrus did not get angry, which was strange to Sans. Whenever he'd sleep on the job, Papyrus usually would tell him to get up and call him "lazybones". Sans was basically the laziest person Papyrus ever knew. But, Papyrus merely said. "ALRIGHT SANS."

Sans raised an eyebrow (or…lack of) and said "wait…that's it? no "lazybones"? no "put your backbone into it"?" Then, he did what he did best. "i'd always thought you didn't like to be humerous with my laziness, pap." When Papyrus only breathed in and out a frustrated sigh, Sans knew something was up. He'd usually HATED his puns; he usually hated ALL puns. Sans had to ask "alright, something wrong. is there something wrong?" Papyrus reassured his brother. "NO, THERE IS NOTHING WRONG; FAR FROM IT, IN FACT. IF YOU WANT TO SLEEP ALL DAY AND…MAKE YOUR PUNS, I WILL NOT STOP YOU. IT'S YOUR BIRTHDAY; I'LL JUST MEET YOU NEAR MT. EBOTT LATER. I HAVE TO…TALK TO YOU…FOR A LITTLE BIT." Papyrus turned to the nearby child. "COMEON, FRISK. WE HAVE TO GET READY." While Papyrus was walking out the door, Frisk walked to Sans instead. The child pulled something out of their pocket and gave it to Sans. Sans slowly accepted the tiny dark blue box and said "oh…thanks frisk." Sans noticed that the box held a tiny note on the outside, which read "Don't open until your actual birthday."

Papyrus said "COMEON, FRISK. WE MUST GET READY FOR THE SUPER BIG SURPRISE THAT SANS IS UNAWARE ABOUT!" Then, Frisk left the room, but Papyrus looked back to Sans. "OH…AND SANS…YOU WERE WRONG ABOUT BEFORE…YOU ARE THE BEST BROTHER ANYONE COULD ASK FOR." Then he finally left the room, leaving only Sans.

Sans looked at the floor while sitting on his bed and sighed. He turned his head to the mirror Papyrus hung on his wall a couple of days ago. He was face to face with his reflection. "trust me…" Slowly but surely, the mirror showed that his hands started to glow a bright neon blue, and his left eye began to glow the same color. "…i'm not."


	3. Chapter 2

Chapter 2

Darkness…that's all Sans could see. He couldn't even look at his hands. He didn't remember waking up to this, it just…happened. While walking blindly through the thick darkness, he could see something…little specks of white. Without anywhere else to go, Sans had to walk towards them. While walking, the specks slowly formed into something…two hands…two hands with holes inside? Then, the biggest speck…a face…a familiar face…No…no it can't be. Sans stopped walking for a moment, something about the figures eyes just hypnotized him…because they were familiar.

"g-gaster?"

As soon as he said that name, the face charged towards him, causing him to wake up. Sans sat up with sweat almost soaking his clothes and the sheets on his bed. His breaths were extremely quick and were synchronizing with his rapid heartbeat.

After a couple of seconds, Sans' hands and eye started to charge and glow again. This time, however, it felt more powerful. It was not that Sans himself actually FELT powerful, far from it, it was something…or someone…MAKING him more powerful. Then, on the corner of his eye, something started floating off of his dresser…and it didn't have a SOUL.

Sans began to sweat even harder and he started breathing more rapidly as his SOUL glowed through his body, showing a large, indigo heart on his chest. Sans had NEVER made a thing without a SOUL levitate before! It really scared him, even to the point of him shivering.

Soon, more stuff on the dresser started floating, and later the entire dresser was off the ground. As his heartbeat got more rapid and his sweat soaked more of his clothes and sheets, he felt something push up beneath him. Sans noticed that the bed was actually glowing blue and off the ground along with everything else in the room. After noticing this, Sans' breaths started turning into screams. He had to stop this before something worse would happen! When he tried moving his hands, he made the levitating objects move his actions, including his bed. Quickly, he started swiping his hands down, in hopes that all of the stuff would go back to normal gravity. Thankfully, it worked, but not in the way he wanted. The objects went back to the ground so suddenly that some of them shattered on the floor.

His hands then started to calm down as he calmed down. It was a slow process, but his hands and eye eventually died down. Sans got up, still shivering, and started quickly picking up his mess, sweat still covering his bones.

He can't believe that happened. He didn't lose control of his powers that badly since…that day. Sans wondered if this had to do with him aging. Maybe because he was turning 18, his powers were starting to get more powerful, making him unable to control it. It's like…magic puberty (if that's even a thing). It doesn't matter what caused it or not, anyway, he needs to get control of his abilities before it gets out of hand…like last time.

Sans picked up all of his broken properties and put them into the trash. Then he picked up the present Frisk got him earlier. Thankfully it didn't break, nor did the top fall off, so the present wasn't spoiled. Sans smiled at the present and put it on his dresser, which he had to pick up without using his powers (which was NOT an easy task). While he was placing the present on his dresser, he looked at the clock, which read 2:53.

"oh no…have i really slept that long?!" Sans thought out loud. He quickly rubbed his face with a spare cloth he had on the desk to wipe his nervous sweat off. As he went out the door to get to Mt. Ebott, he thought about his brother. "i'm sorry i'm late, papyrus. guess this just has to be yet another secret I have to keep from you."

All of these moments were being watched, not by Gaster, buy by another…even more darker entity.

"So…he has finally showed his true power. And he still wants to keep it from his brother just to protect him. Daaw. So adorable." The entity's fake frown turned into an incredibly real smile. "Don't worry Sans, I'll make sure that your powers will be shown."

The entity went from Sans' house, from Ebott City, to the peak of Mt. Ebott, to the inside of Mt. Ebott. Finally, the spirit came across an old friend, their only friend. A wilted plant, with burn marks all over itself, with other perfect yellow flowers surrounding it. "Flowey." The yellow flower turned to his friend and plastered an evil grin across his face. "Chara."

Chara walked towards Flowey, crushing the pretty flowers under their feet as they walked. Flowey looked at their cold eyes and said "It's been a long time since I've actually seen you." Chara replied "I am aware of that. Anyways, I have learned something that you might be interested in." Flowey got curious. "Oh yea, and what might that be?" The child-like demon smiled evilly and answered "You remember our dear friend Sans, correct?"


	4. Chapter 3

_Oh, greetings._

 _It's been a while since we last saw you!_

 _We've been waiting for you for a long time!_

 _Yep! We waited for you even if you made a HUMONGOUS mistake last time._

 _So…_

 ** _What took you so long?_**

Sans hurriedly hopped on his bicycle and placed his bones on the handles. He looked to his right to see the gigantic form of Mt. Ebott covered by an extremely light.

Mt. Ebott has always been a huge landmark, so big that you could see it from the town. Legend has it that ever since the monsters were trapped there, the human king decided to call the land the two species shared their own. The human king called it "Ebott City"… Hey, at least that king was more creative than King Asgore. Sans had to face it, despite how great and kind his king was, he can be pretty oblivious at times. Well, not as oblivious as his brother.

…Oh crap! He needs to stop daydreaming and go!

Sans quickly pedaled his way to the peak of Mount Ebott. Unfortunately, a hiking human family managed to spot him, and they just…looked at him. They didn't yell they didn't call him names; they didn't even look at him the wrong way. But Sans knew what they were thinking. "Man, isn't it weird that monsters exist now?"

Whatever, thought Sans, it's so typical that the monsters aren't even afraid of it anymore. Sans shook his head and continued pedaling to the inside of the mountain.

Meanwhile, at the inside of Mt. Ebott, there was a strange commotion coming from inside. The humans that were hiking heard the music and decided to go see what it was. When they got near the top, they saw a small mouse with a green scarf over his nose and mouth and a gigantic…umm…'snowflake bird?' was going into Mt. Ebott. Not wanting to see the other hideous monsters, they decided to go back down, completely ignoring the gigantic birthday party that was going on inside the mountain.

Every single monster was in the highest peak of Mt. Ebott, with Muffet's baked goods being eaten and Napstablook's music blasting in the background. Almost all of the monsters were dancing, chatting with their friends, and all around having an awesome time…that is except for a few people.

Burgerpants was stuck in the corner of the peak trying to sell his fast food, which was well after frozen at that point. Needless to say, he was having an especially hard time to keep a straight face. Monster Kid kept on getting bumped around by the dancing creatures on the dance floor, so he decided to sit near one of the tables and rest for a while. Even Frisk was off the dance floor, which was…a weird thing for Frisk to do. They would've liked to dance with their monster friends while enjoying Muffet's spider web covered sweets. The only thing that was holding Frisk back from doing so was the fact that Papyrus was pacing back and forth near Monster Kid's table, his gloved hand placed on his chin.

"NOW WHAT HAPPENED TO SANS?! HE WAS SUPPOSED TO BE HERE OVER AN HOUR AGO! THAT LAZYBONES MUST BE NAPPING! OR FINDING OTHER EXCUSES TO BE LAZY! OR…DOESN'T WANT TO GO TO THE PARTY AFTER ALL…OR WORSE! HE MUST BE BUSY THROWING ME AND UNDYNE'S SPAGHETTI AWAY!" Papyrus stopped and put his hands on his head in the thought. "OH GOD NO!"

Frisk rubbed Papyrus' shoe, trying to calm him down. Papyrus took notice and looked at down at them. "OH HUMAN! THANK YOU KINDLY FOR TRYING TO COMFORT MY BOOT. IT REALLY APPRECIATES YOUR KIND GESTURE. BUT EVEN THAT COULDN'T HELP." Papyrus leaned down at Frisk's level with his arm rested on one knee. "YOU SEE FRISK. THERE'S THIS…CEREMONY THAT HAPPENS WHEN A SKELETON TURNS EIGHTEEN YEARS OF AGE. IT'S A VERY IMPORTANT EVENT THAT CONFIRMS A SKELETON'S RISE FROM TEENAGE YEARS INTO ADULTHOOD. AND, HOPEFULLY ONCE THE EVENT IS OVER, SANS WOULD FINALLY LEARN THE IMPORTANCE OF BEIN G RESPONSIBLE AND TAKING CARE OF HIMSELF." Out of nowhere, a rough voice spoke up. "Pfft, yea. Like Sans would ever stop napping on duty."

Papyrus stood up and turned to see that the voice belonged to Undyne, leaning on one of the sides of Monster Kid's table with her arms crossed. Frisk noticed her friend's presence and ran up to her so they could hug Undyne. Undyne stood up from the surprising embrace and looked down at them with her arms raised. "Whoa! OK, what's with the hugging? Is this supposed to be some kind of attack?! If so…I admire your element of surprise!"

Papyrus spoke. "UNDYNE! YOU FINALLY CAME! WHAT TOOK YOU SO LONG?!" Undyne put her head up to look at her skeleton trainee. "Sorry. Had to help Alphys with something important she's working on for Sans' party." Papyrus got curious and walked towards her. "REALLY? WOWIE! WHAT IS IT?!" Undyne put on her signature grin and replied "You'll see…"


	5. Chapter 4

_Oh dear…_

 _Yet another long break._

 _Granted not as bad as other timelines, but still bad._

 _I mean, the cowards won't be entertained without a little adventure to watch._

 _So this time, don't make the same mistake again._

 _I'll be keeping an eye on you, Ms. Author._

The abandoned lab was still and quiet, just like an abandoned lab should be. Except, something was…different.

It's hard to put a finger on it, but it's just different.

Flowey had bad memories of this place, which was strange, since he was technically created here, but the Almalgamates made everything so…eerie. Alphys practically holding him captive didn't make things better. He had no choice to interact with the other failures while the Royal Scientist just sat around and watched Kissie Cutie Meow-whatever the hell it was.

Flowey was just glad he escaped while he could (with a little help from his RESET power) so he could finally be free and create all the havoc that he wanted…One of his worst pet peeves was going back.

But for this certain plan he and Chara were planning, he had to go back; it was just too glorious to ignore. Flowey would do anything to take his place in the throne…even if it means breaking reality.

Flowey went to the gigantic dragon-like skull that was lifted up by some wires in the ceiling. The demonic flower still didn't know what the purpose of it was, even though he saw it almost every day when he was in the lab. But, from what Chara told him, it was the invention of an old Royal Scientist…the exact same scientist he was told to contact.

Flowey approached the skull, vile of leftover DETERMINATION in his vines. "Hey, Mr. Scientist. I have an offer for you. I can't exactly see you, since you're…kinda in another plane of existence, but I'm assuming you followed the DETERMINATION I left out for you from Waterfall. I mean, it is your own invention after all, right?" Flowey clutched at the nearly empty vile, hoping this guy was actually real and he wasn't making himself look even more insane than he already was.

"Anyway, I was thinking we could talk about a few things…maybe even a few people you might recognize..." Flowey's face turned sadistic in the thought.

"Does 'Sans the Skeleton' ring a bell?"

Suddenly he felt the universe crash on him, as his surroundings became distorted. Static came exploding out of the floor and walls, causing Flowey to become dizzy. The chaos stated to calm down as a large black and white hole began to form and a certain white face emerged.

Flowey started at the figure in the portal and his smile became even more demonic. "So, let's make a deal."

The white face of Gaster mimicked Flowey, making the most sinister smile the being has ever produced.


End file.
